6,555 research outputs found
Improving LMA predictions with non-standard interactions: neutrino decay in solar matter?
It has been known for some time that the well established LMA solution to the
observed solar neutrino deficit fails to predict a flat energy spectrum for
SuperKamiokande as opposed to what the data indicates. It also leads to a
Chlorine rate which appears to be too high as compared to the data. We
investigate the possible solution to these inconsistencies with non standard
neutrino interactions, assuming that they come as extra contributions to the
and vertices that affect both the
propagation of neutrinos in the sun and their detection. We find that, among
the many possibilities for non standard couplings, only the diagonal imaginary
ones lead to a solution to the tension between the LMA predictions and the
data, implying neutrino instability in the solar matter. Unitarity requirements
further restrict the solution and a neutrino decay into an antineutrino and a
majoron within the sun is the one favoured. Antineutrino probability is however
too small to open the possibility of experimentally observing antineutrinos
from the sun due to NSI.Comment: 27 pages, 8 figures. Final version to be published in Physical Review
Improving LMA predictions with non standard interactions
It has been known for some time that the well established LMA solution to the
observed solar neutrino deficit fails to predict a flat energy spectrum for
SuperKamiokande as opposed to what the data indicates. It also leads to a
Chlorine rate which appears to be too high as compared to the data. We
investigate the possible solution to these inconsistencies with non standard
neutrino interactions, assuming that they come as extra contributions to the
and vertices that affect both the
propagation of neutrinos through solar matter and their detection. We find
that, among the many possibilities for non standard couplings, only one of them
leads to a flat SuperKamiokande spectral rate in better agreement with the data
and predicts a Chlorine rate within 1 of the observed one, while
keeping all other predictions accurate
An empirical analysis of structural models of corporate debt pricing
This paper tests empirically the performance of three structural models of corporate bond pricing, namely Merton (1974), Leland (1994) and Fan and Sundaresan (2000). While the first two models overestimate bond prices, the Fan and Sundaresan model reveals an extremely good performance. When considering the prediction of credit spreads, the three models under-estimate market spreads but, again, Fan and Sundaresan has a better performance. We find rating, maturity and asset volatility effects in the prediction power, as the models under-estimate less the spreads of riskier firms and of bonds with better rating quality and longer maturity. Moreover, our results reveal the existence of a new industry effect. Spread errors are systematically related to some bond- and firm-specific variables, as well as term structure variables.structural models, corporate debt valuation, empirical credit spreads
Neutrino Mass Matrices with Vanishing Determinant and
We investigate the prospects for scenarios with vanishing determinant
neutrino mass matrices and vanishing mixing angle. Normal and
inverse mass hierarchies are considered separately. For normal hierarchy it is
found that neutrinoless double beta decay cannot be observed by any of the
present or next generation experiments. For inverse hierarchy the neutrinoless
double beta decay is, on the contrary, accessible to experiments. We also
analyse for both hierarchies the case for texture zeros and equalities between
mass matrix elements. No texture zeros are found to be possible nor any such
equalities, apart from the obvious ones.Comment: 14 pages, 1 figur
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